1. Field of the Invention
The present invention relates to the technology of image pickup elements capable of optically receiving photographic-subject light beams passing through exit pupils of photographic optical systems.
2. Description of the Related Art
In image pickup devices, such as single-lens reflex cameras with interchangeable lenses, image pickup elements capable of performing focus detection based on a phase-difference detection method are used. An image pickup element of this type will sometimes be referred to as “image pickup element having a phase-difference detecting function” hereinafter. Specifically, in an image pickup element having a phase-difference detecting function, a pair of photoelectric conversion portions (photodiodes) that generate pixel signals by optically receiving photographic-subject light beams passing through a pair of segmental regions (for example, left and right pupil segments) in an exit pupil of an interchangeable lens (photographic optical system) is provided in a plurality. The following are examples of such image pickup elements of the related art.
For example, Japanese Unexamined Patent Application Publication No. 2001-250931 discloses an image pickup element having a phase-difference detecting function, in which bisected-like photoelectric conversion portions (referred to as “half-sized photoelectric conversion portions” hereinafter) are provided in each of normal pixels (R, G, and B pixels) that acquire image signals of a photographic subject. In other words, a pair of half-sized photoelectric conversion portions is disposed below each micro-lens.
Japanese Unexamined Patent Application Publication No. 2005-303409 discloses another example of an image pickup element having a phase-difference detecting function, which limits photographic-subject light with small openings in a light-blocking mask made of a metallic layer in a pair of neighboring pixels so as to optically receive a pair of segmental regions in the exit pupil with a pair of photoelectric conversion portions.